Solvent refining of light oils



80 to 120 F. to form tertiary.water-rich and Patented May 16, 1950 SOLVENTIREFINING OF LIGHT OILS -Robert E. Manley, Yonkers, N. Y., 'assignor to The Texas-Company, New York, N. Y., -a corporation of Delaware No Drawing. 'Applicationlluly 21, .1948, Serial No. 40.0.06

,1 Claim. (Cl. 196-1426) This invention-relates to the refining of lowboiling oil'with aselective solvent for the production of valuable products such as Diesel oil.

'iThe present application is a continuation-inpart 01' my pending application Serial No. 778,833, filed October 9, 1947, now Patent No. 2,475,147, for improvements in Solvent refining of lightoils.

'In the pending application, I have disclosed extracting a feedoil suchas'gas oil'derived from the catalytic cracking of'gas'oil' from California crude oil with a selective solvent such as furfural underconditions effective "'to'form extract and raflinate phase "mixtures. "The rafiinate phase mixture comprises non-aromatic:or relatively insolubleconstituents'of the-oil mixed with a small proportion of the solvent. The extract phase mixture: comprises relatively aromatic, non-paraflinic and more soluble constituents of the oil dissolved in the main body of solventliquid.

These extract and raifinate mixtures are separately subjected to fractional distillation with the aid of steam, the distillation being azeotropic or partially azeotropic in character so as to strip the solvent completely or substantially. completely from the oil while "avoiding excessive carrying over of low-boiling constituents of the oil in the 'di'stillates. The resulting distillates are either separately condensed-"or condensed-in the presence of each other. The resulting condensed liquid or liquids comp-rising solvent and relatively small amounts of oil and-water are thereafter subjected to a primary settling wherein soil-rich,

water-rich and solvent-rich liquid .layersare obto form secondary. oil-rich andsolvent-rich'liquid layers respectively. :This secondary solvent-rich liquid is recycled. and commingled .withi.lthe-./pri- .mary solvent-richliquid layer.

The secondary oil-rich liquid as well astheprimary oil-rich liquid. is subjected to washing by contact with. a relatively largeproportionof water .ata temperature sufficiently elevated to .effect extraction by the water of residualsolvent .re-

emaining in the-secondary oil. ...'Ihe resulting washedoilis discharged from the system.

The resulting solution of residuaLsolventand wateris subjected .toa tertiary settlingata' low temperature, for example,v in the. range. of about solvent-rich layers respectively. .The tertiary solvent -richliquid recycled. and commingled with thecondensatepassing to the primary settleingazone, while the. tertiary. water-rich .liquid .as

well as the primary water-rich liquid is subjected to a secondary fractionating step whereinthe-wet solvent is concentrated and from whichsolventfree water is discharged asaresidual liquid fraction. The'secondary distillate of increased-solvent content is'condensed and recycled tothe tertiary-settling zone.

The present invention is particularly concerned with the "production of-a desulfurized oil suitable "for'Diesel fuel from a-high sulfur content gas-oil by first subjecting the feed oil to the action-of a cracking catalyst under cracking conditions. The resulting cracked gas oil orportion of'the 'crackedproduct boiling in'the range *ofgasoil is then subjected to solvent refining with a solvent such as furfural to remove sulfur and nitrogen bodies and-relatively aromatic hydrocarbons leavingxa refined oil-of paraffinic character and of 'materially'reduced sulfur and nitrogencontents.

The invention 'is particularly applicable 'to-the treatment of high sulfur content gas oils'suchas derived from California crudes. This typeof gas oil isrelatively high'in'sulfur content-andthe sulfur compounds are difficult to removebysolvent extraction.

I have discovered that by subjecting high sulfur content gas -0i1.of the type inxquestion: to the action of an alumina-silica cracking :catalyst maintained under cracking conditions, the refractory sulfur compounds undergo conversion so that they are more susceptible to removal by solvent :extraction with a solvent such as furfural.

For aexamplaa residual crude obtained from California petroleum was subjected to viscosity breaking by passage through a pipe still at a temperature ofabout'SOO to850 F. and under a pressureof about .40 to 60 lbs. gauge. The pipe still :eifiuent was. fractionated to produce a gas oil having the following.characteristics:

.This:gas-oil"was then subjected to liquid-liquid extraction 'witn'furfural' saturated with water, the extraction being eilected at a temperature of about F. employing xone-halfvvolume; ofsolvent per-volume of gas oil. .The. resulting extract and raffinatephaseswere separatediand thegsolvent 'removed therefrom. Theusolvent-iree. rafto the solvent extraction step and this refined oil had the following characteristics:

Gravity, A. P. I 26.6 Nitrogen, per cent 0.09 Sulfur, per cent 1.08 Neut. number 0.52

When another sample of this gas oil was extracted under similar conditions with the same type of solvent but employing one volume of solvent per volume of gas oil the refined oil yield amounted to 85.2% of the gas oil and the sulfur content of this refined oil was 1.06% or substantially similar to the sulfur content of the refined oil previously obtained.

The significant fact is that the solvent refining of this gas oil even though it had been exposed to thermal decomposition in the pipe stilling operation did not materially reduce the sulfur content. That is to say, the sulfur content was around 1.06 to 1.08% as compared with 1.29% for the feed oil.

By contrast, gas oil approximately similar to that obtained in the pipe still operation was subjected to catalytic cracking in vapor phase by contact with a fluidized alumina-silica catalyst at a temperature of about 960 F. and under atmospheric pressure employing a space velocity of about 1.65 volumes of liquid hydrocarbon feed per volume of catalyst per hour. Under these conditions a substantial proportion of the feed oil was converted to gasoline hydrocarbons. Thus the gasoline and lighter material obtained amounted to about 50% by volume of the gas oil feed.

The products of this catalytic cracking were fractionated to obtain therefrom a cracked gas oil fraction of the following characteristics:

Gravity, A. P. I 26.8 Sulfur, per cent 0.54 Cetane number 33.4

A. S. T. M. distillation:

I. B. P F 430 F 474 F 486 50% F 513 90% F 584 End point F 662 This cracked gas oil was subjected to solvent extraction with furfural saturated with water, the extraction being efiected at a. temperature of about 77 to 90 F. employing about 0.66 volume of solvent per volume of cracked gas oil feed. The resulting extract and raifmate phase mixtures were separated and the solvent recovered therefrom. The resulting solvent-free raflinate oil amounted to by volume of the cracked gas oil feed and had the following characteristics:

Thus it is seen that the solvent extraction of the catalytically cracked oil resulted in a very much greater reduction in the sulfur-content. Thus the sulfur-content of the refined oil was 0.16% as compared with 0.54 for the cracked feed, oil.

' 1 mol of alumina.

It appears that the catalytic cracking action not only very greatly reduces the sulfur content, for example, from 1.29% down to about 0.54%, but also renders the remaining sulfur compounds in the catalytically cracked oil more susceptible to removal by solvent extraction. The refined oil product obtained is also characterized by a relatively high cetane number. It is very suitable for the manufacture of Diesel fuel oil.

Furthermore, the sulfur removal with solvent extraction is enhanced by a more drastic catalytic cracking treatment. Thus, the same feed stock when cracked to a conversion of about 60% produces a catalytic cycle gas oil even more susceptible to solvent treatment.

A catalytic cycle gas oil of the following characteristics resulted from deeper crackingz.

Gravity, A. P. I 25.1 Sulfur 0.55 Cetane number 31 A. S. T. M. distillation:

I. B. P F 430 10% F 480 20% F 496 50% F 526 .F' 598 End point F 672 Using approximately the same volume of solvent at similar conditions of counterfiow extraction the refined oil yield amounted to 47% by volume of the cracked gas oil feed and had the following characteristics:

Gravity, A.'P. I 38.7 Percent Sulfur 0.08 Cetane number 56 A. S. T. M. distillation:

I. B. P F 414 10% F 456 20% F 4'72 50% F 515 90% F 596 End point F 644 It will be noted that although the refined oil yield is lower the cetane number increase and the sulfur reduction are both greater than with the product representing a lower conversion of the virgin gas oil.

The catalytic cracking operation decomposes the nitrogen compounds and hence the amount of nitrogen remaining in the cracked gas oil'is negligible.

Thermally cracked gas oil is inferior for Diesel manufacture for the further reason that it has a much heavier A. P. I. gravity and contains less material of high cetane value.

Effective catalytic cracking catalysts are those comprising from about 5 to 20 mols of silica to Either naturally occurring or synthetic alumina-silica catalysts may be employed, the catalyst being substantially free from alkali metal compounds. An effective synthetic catalyst comprises essentially a calcined mixture of hydrated silica-alumina gels. The hydrated silica gel may be mixed while in a wet condition with separately prepared hydrated alumina, or the gels may be coprecipitated. The mixture may also contain a small amount of zirconium oxide or other metal oxides within the range of about 2 to 6 mol per cent of the silica.

The cracking reaction may be carried out at a temperature ranging from about 800 to 1000 F. using the fluidized'solids techniquewherein ketones, phenols, etc.

the vaporized feed oil is passed upwardly through a fluidized mass of the catalyst in solid particle form. In other words, a conventional fluidized catalyst cracking operation may be employed such as disclosed for example, in U. S. 2,425,482, granted to C. E. Moser on August 12, 1947.

Other high boiling organic solvent liquids besides furfural may be employed including derivatives of the furan group as well as other compounds such as benzaldehyde, nitrobenzene, The solvent extraction may be carried out in a conventional manner employing liquid-liquid extraction with countercurrent flow between oil and solvent, or extractive distillation may be employed. Liquid-liquid extraction with furfural or with furfural containing a small amount of water is usually carried out at substantially amospheric pressure and at a temperature within the range of about 70 to 150 F.

Although mention has been made of applying the process to the treatment of gas oils obtained from California crudes nevertheless it is contemplated that it may be applied to other feed stocks having high sulfur and also high nitrogen contents for the production of Diesel oils and other products of low sulfur and nitrogen contents.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated in the appended claim.

I claim:

A method of producing Diesel fuel oil from re- 3 prises subjecting said reduced crude to heating at a temperature of about 800 to 850 F. while under super atmospheric pressure such that the feed oil undergoes thermal cracking suflicient to reduce substantially its viscosity, distilling from the thermally cracked crude a fraction boiling in the range of gas oil, subjecting said gas oil fraction While in vapor phase to contact with a fluidized alumina-silica cracking catalyst at a temperature of about 960 F. and under about atmospheric pressure such that at least about by volume of the gas oil is converted into gasoline and lower boiling material, fractionating from the products of catalytic cracking a second gas oil fraction, subjecting this second gas oil fraction to solvent extraction with furfural saturated With Water at a temperature of about 77-90 R, such that raffinate oil and extract oil fractions are formed, withdrawing said raffinate oil fraction and stripping residual solvent from the withdrawn fraction thereby obtaining solvent-free raffinate oil substantially free from nitrogen, containing not in excess of about 016% sulfur and having a relatively high octane number.

ROBERT E. MANLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,228,510 Dearborn et al Jan. 14, 1941 2,342,888 Nysewander et al. Feb. 29, 1944 2,429,875 Good et al. Oct. 28, 1947 2,431,243 Greensfelder et a1. Nov. 18, 1947 

